B Keerthika¹, Y P Cao², D Raabe¹

CMC-Computers, Materials & Continua, Vol.10, No.3, pp. 243-258, 2009, DOI:10.3970/cmc.2009.010.243

Abstract In this study, effects of the plastic deformation and the time-dependent deformation behavior on the fundamental relations in the Oliver & Pharr method are studied by using finite element analysis based on a viscoelastic-plastic model developed for polymers. The study eventually yields an experimental protocol and using which, the instantaneous modulus of the viscoelastic-plastic materials may be reliably determined. Experiments have been performed on four polymers to verify the conclusions from the numerical analysis. More >

A. Sellier¹

CMES-Computer Modeling in Engineering & Sciences, Vol.25, No.3, pp. 165-180, 2008, DOI:10.3970/cmes.2008.025.165

Abstract The slow viscous and either imposed or gravity-driven migration of a solid arbitrarily-shaped particle suspended in a Newtonian liquid bounded by a spherical cavity is calculated using two different boundary element approaches. Each advocated method appeals to a few boundary-integral equations and, by contrast with previous works, also holds for non-spherical particles. The first procedure puts usual free-space Stokeslets on both the cavity and particle surfaces whilst the second one solely spreads specific Stokeslets obtained elsewhere in Oseen (1927) on the particle's boundary. Each approach receives a numerical implementation which is found to be in More >

Pravin Subramanian¹, Abdelfattah Zebib¹

FDMP-Fluid Dynamics & Materials Processing, Vol.4, No.3, pp. 139-162, 2008, DOI:10.3970/fdmp.2008.004.139

Abstract A theoretical and computational study of solutocapillary driven Marangoni instabilities in small spherical shells is presented. The shells contain a binary fluid with an evaporating solvent. The viscosity is a strong function of the solvent concentration, the inner surface of the shell is assumed impermeable and stress free, while non-linear boundary conditions are modeled and prescribed at the receding outer boundary. A time-dependent diffusive state is possible and may lose stability through the Marangoni mechanism due to surface tension dependence on solvent concentration (buoyant forces are negligible in this micro-scale problem). The Capillary number (Ca) provides More >

Ren Jiusheng¹

CMC-Computers, Materials & Continua, Vol.7, No.1, pp. 25-32, 2008, DOI:10.3970/cmc.2008.007.025

Abstract Elastic instability for the inflation and deflation of a thin-walled spherical rubber balloon is examined within the framework of finite pseudo-elasticity. When a spherical rubber balloon is inflated, it is subject to a complex deformation after a pressure maximum has been obtained. One part of the balloon is lightly stretched while the remainder becomes highly stretched. So an aspherical deformation is observed after the initial spherical inflation. A pseudo-elastic strain energy function including a damage variable which may model the loading, unloading and reloading of rubber is used. The balloon is idealized as an elastic More >

K.Y. Volokh ¹

CMC-Computers, Materials & Continua, Vol.3, No.1, pp. 37-42, 2006, DOI:10.3970/cmc.2007.003.037

Abstract Lagrangian or referential equilibrium equations for materials undergoing large deformations are of interest in the developing fields of mechanics of soft biomaterials and nanomechanics. The main feature of these equations is the necessity to deal with the First Piola-Kirchhoff, or nominal, stress tensor which is a two-point tensor referring simultaneously to the reference and current configurations. This two-point nature of the First Piola-Kirchhoff tensor is not always appreciated by the researchers and the total covariant derivative necessary for the formulation of the equilibrium equations in curvilinear coordinates is sometimes inaccurately confused with the regular covariant derivative. More >

J.M.M. Sousa¹

CMES-Computer Modeling in Engineering & Sciences, Vol.9, No.2, pp. 211-220, 2005, DOI:10.3970/cmes.2005.009.211

Abstract Time-dependent numerical simulations of the flow through a spherical bulge in a 90-degree asymmetrical bend have been performed for Reynolds numbers in the range 100-400. The present results have demonstrated that the flow reaches asymptotically steady, symmetrical solutions for Reynolds numbers up to 300, whereas a value of 400 for this parameter leads to unsteadiness. The computed flow behavior at this higher Reynolds number has shown to be characterized by an intermittent transition between small-amplitude, irregular oscillations and large-amplitude bursts occurring at a low frequency. In addition, the unsteady flow was asymmetrical and exhibited swirl More >

S.-C. Hsiao¹, M.S. Ingber²

CMC-Computers, Materials & Continua, Vol.1, No.1, pp. 51-58, 2004, DOI:10.3970/cmc.2004.001.051

Abstract The lateral migration of nonneutrally-buoyant spherical particles in Poiseuille flow is investigated numerically using the boundary element method. In particular, the steady, Navier-Stokes equations are solved using a classical domain integration method treating the nonlinear terms as pseudo-body forces. The numerical results for the lateral migration velocity are compared with experimental data. The numerical results indicate that the lateral migration velocity does not scale linearly with the Reynolds number. The methodology is extended to include non-Newtonian power-law fluids. The migration velocity is significantly affected for particles suspended in this class of fluids and can actually More >